Telephone interconnecting circuit



Jan. 23, 1934. F. STRECKER 1,944,283

TELEPHONE INTERCONNECT ING CIRCUIT Filed May 31, 1930 lNl/ENTOR I. STREC/(ER ATTORNEY Patented Jan. 23, 1934 TATES TELEPHONE INTERCONNECTING CIRCUIT Felix Strecker, Berlin-Steglitz, Germany, as-

signor to Siemens & Halske Aktiengescllschaft, Siemensstadt, near Berlin, Germany, a compenny of Germany Application May 31, 1930, Serial No. 458,441, and in Germany June 22, 1929 3 Claims.

The present invention relates to interconnecting circuits for telephone lines or similar circuits. The invention has particular reference to the socalled conference type of connection in which 5 three or more subscribers lines are interconnected so that each may communicate simultaneously with all the others.

An object of the invention is to associate three or more telephone or similar circuits by a simple and direct scheme of interconnection providing conjugacy between the transmitting and receiving terminals of each line.

A feature of the invention is the use of an interconnecting network in the form of a polygon in which the sides of the polygon are used for transmitting and the diagonals for receiving.

The polygon preferably has as many sides as there are circuits or lines to be interconnected. The impedances of the respective sides of the network of polygon form are preferably equal and the impedances of the diagonals are also equal, thus providing mutually equal attenuation for all the subscribers.

. Referring to the drawing,

Fig. 1 discloses a diagram showing the fundamental principle of interconnection according to the invention; and

Fig. 2 discloses one type of circuit for putting the principle of the invention into operation.

Fig. 1 shows a polygon of five sides although this polygon may be considered as having N sides where N is any odd number greater than four. The sides of the polygon hl to hs are intended in this figure to represent equal impedances which are connected in series to form a complete polygon of impedances. The apices 1 to 5 areall connected with each other by diagonals n to m respectively.

If a source of E. M. F. is connected between the adjacent apices, for example, the source h]. between the apices 1 and 2, then all of the other (N minus 2) apices have the same potential, a potential which is mid-way of that between the points 1 and 2, that is, the points 3, 4 and 5 are each at the mid-potential existing between points 1 and 2.

The diagonal 11, therefore, connects points of equal potential (3 and 5) and is conjugate with respect to the source of E. M. F. in the side hi.

Each of the other diagonals r2, r3, r4, r5, however,

has impressed upon it an E. M. F. equal to onehalf that of the transmitting source in the side h1.

If the transmitting terminals of a telephone line be connected in the side h1, therefore, and the receiving terminals across the diagonal r1 these two sets of terminals are conjugate to each other.

If the same scheme of connection is carried out for the four other lines the receiving branches T2 to T5 of the other lines will each receive an E. M. F. from the transmitting branch h1 of the first line.

In this way each line directly transmits to all of the other lines but there is no feed-back or return voltage appearing at the receiving side of any given line.

The scheme of interconnection shown in Fig. 2 follows directly from what has been described above of Fig. 1. Each of the five two-way lines Z1 to Z5 is provided with a corresponding balancing network in to 725 and hybrid coil m to as. 7 The transmitting branch of each line is connected into one of the sides of the polygon, that is, in the position hl, 7L2, etc. If desired, each such transmitting branch contains an amplifier '0.

Each receiving branch leading to the hybrid coil (11, :12, etc., is connected in a diagonal r1, 12, etc., which may likewise, if desired, contain an amplifier 0. As in Fig. 1, the receiving branch of each line is connected to the proper diagonal of the network to make the receiving branch conjugate with respect to the transmitting branch of that line.

The five sided polygon may also be used Where only four subscribers lines are to be interconnected. This may be done by replacing certain of the two-wire lines of Fig. 1 or 2 by suitable resistances or impedances which simulate an actual line. In Fig. 2, for example, line Z4 may be removed from the network by shifting the four switches s1, s2, s3 and st to their alternate contacts so that an impedance 21 is substituted in diagonal 1'4 for the transmitting impedance offered by line Z4 when present ande'z is substituted in the side hi for the receiving impedance of the line. In the same way other lines may be disconnected and replaced by equivalent impedances. The principle of the invention illustrated and described in connection with Figs. 1 and 2 may, as already stated, be extended to a greater number of subscribers lines than five. In this latter case also, diagonals or sides which it is not desired to use for the transmitting or receiving branches of a line may be replaced by suitably proportioned resistances.

What is claimed is:

1. A scheme of interconnection of more than three transmission circuits each having transmitting terminals and receiving terminals, in which the transmitting terminals of the circuits are connected in series to form a complete polygon I15 branches have their respective terminals connected in seriatim to form a complete polygon of equal impedances, and the receiving branches are connected to the appropriate diagonals to make the transmitting and receiving branches conjugate in the case of each line.

3. A system according to claim 1 in which certain of the impedances representing sides of the polygon are impedances substituted for actual lines.

FELIX STRECKER. 

